| Subject | Re: [PATCH 4.16 008/161] packet: in packet_snd start writing at link layer allocation | From | Tariq Toukan <> | Date | Thu, 24 May 2018 17:53:15 +0300 |
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On 24/05/2018 12:37 PM, Greg Kroah-Hartman wrote: > 4.16-stable review patch. If anyone has any objections, please let me know. >
Please hold on with this. I think it causes some degradation.
I'll report the issue on the original patch.
Thanks, Tariq
> ------------------ > > From: Willem de Bruijn <willemb@google.com> > > [ Upstream commit b84bbaf7a6c8cca24f8acf25a2c8e46913a947ba ] > > Packet sockets allow construction of packets shorter than > dev->hard_header_len to accommodate protocols with variable length > link layer headers. These packets are padded to dev->hard_header_len, > because some device drivers interpret that as a minimum packet size. > > packet_snd reserves dev->hard_header_len bytes on allocation. > SOCK_DGRAM sockets call skb_push in dev_hard_header() to ensure that > link layer headers are stored in the reserved range. SOCK_RAW sockets > do the same in tpacket_snd, but not in packet_snd. > > Syzbot was able to send a zero byte packet to a device with massive > 116B link layer header, causing padding to cross over into skb_shinfo. > Fix this by writing from the start of the llheader reserved range also > in the case of packet_snd/SOCK_RAW. > > Update skb_set_network_header to the new offset. This also corrects > it for SOCK_DGRAM, where it incorrectly double counted reserve due to > the skb_push in dev_hard_header. > > Fixes: 9ed988cd5915 ("packet: validate variable length ll headers") > Reported-by: syzbot+71d74a5406d02057d559@syzkaller.appspotmail.com > Signed-off-by: Willem de Bruijn <willemb@google.com> > Signed-off-by: David S. Miller <davem@davemloft.net> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > --- > net/packet/af_packet.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > --- a/net/packet/af_packet.c > +++ b/net/packet/af_packet.c > @@ -2903,13 +2903,15 @@ static int packet_snd(struct socket *soc > if (skb == NULL) > goto out_unlock; > > - skb_set_network_header(skb, reserve); > + skb_reset_network_header(skb); > > err = -EINVAL; > if (sock->type == SOCK_DGRAM) { > offset = dev_hard_header(skb, dev, ntohs(proto), addr, NULL, len); > if (unlikely(offset < 0)) > goto out_free; > + } else if (reserve) { > + skb_push(skb, reserve); > } > > /* Returns -EFAULT on error */ > >
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